Building on findings from developmental and exploratory clinical studies, the applicant's K08 study provided empirical validation for a specific and stable preschool depressive syndrome. Alterations in stress cortisol reactivity, and observational evidence of negative affect and anhedonia were found, providing biological as well as objective evidence for the validity of preschool depression. The ongoing R01 aimed to advance these findings by investigating sub-types and developmental characteristics of preschool depression in a large community based study population, over-sampled for mood disorders. An exploratory investigation of mania symptoms was made possible by a NIMH supplement. Replication and extension of findings validating preschool depression were established in this independent sample. Further, preliminary evidence of a valid and robust preschool bipolar disorder also emerged. The ongoing R01 study sample represents the largest developmentally and diagnostically well-characterized population of mood-disordered preschoolers ascertained to date to our knowledge providing a rich resource for longitudinal follow-up. This application proposes to continue this investigation of preschool mood disorders by examining the course and characteristics of N=302 preschoolers for 3 additional diagnostic and developmental assessments annually through school age. The proposed longitudinal study will allow the first investigation of mood disorders, from their earliest known onset during the preschool period, to outcomes at late school- age, compared to disruptive and healthy children. This proposal aims to investigate the effect of age of onset, sub-type and deviations in emotional development on course and outcome of early onset mood disorders. While much is known about the longitudinal course of later childhood mood disorders, there is a gap in the database on the continuities and mediators of outcome from preschool to school age. This developmental transition is critically important to the public health because of the potential for earlier and more effective intervention in these chronic disorders during a period greater developmental and neurobiolgoical change. This study sample containing a high proportion of preschoolers with mood disorders and appropriate controls provides an unprecedented opportunity to bridge this gap in the empirical database. Findings would serve to inform the design of future early intervention trials for mood disorders.